Roof coatings are well known in the art. Roof coatings that involve temperature management typically involve reflection of sunlight to maintain a cool building. To reduce interior temperature and energy use, cool roofs have been used on commercial, industrial, and residential buildings. Cool roofs are made of highly reflective and emissive materials to help roofs absorb less heat. In 2006, cool roof products represented more than 25% of the manufacturers' shipments in the commercial roofing sector and 10% percent in the residential.
The present invention expands the capability of coatings to automatically and autonomously allow heating by transmission of sunlight, and aid in cooling by reflecting sunlight.
The present invention is unique in that it also is made with renewable bio-based oils. While unused oil may be used, the invention takes on greater environmental value by offering an energy conservation use for waste oil.
The bio-based thermochromic coating of the present invention provides a hardened coating that can autonomously respond to outside temperature changes to transmit or reflect infrared sunlight and thus help heat or cool a building as dictated by actual environmental conditions. The focus of the present invention is infrared radiation and this is distinct from prior art that usually focuses on the transmission or reflection of visible light through windows. For example, the use of a thermochromic coating for windows is taught in U.S. Pat. No. 6,440,592, which also instructs on the use of an intermediate layer comprising titanium oxide.
While use of thermochromic materials in coatings is known, the present invention is unique in the mixture of oil and a catalyst that comprises a thermochromic material. The prior art does not describe this coating composition with catalysis serving to lower the polymerization of triglycerides with monounsaturated and polyunsaturated fatty acid chains in the oil while also having a thermochromic property. The combination is unique.
Waste cooking oil is of particular interest in this invention. Waste cooking oil is both a renewable resource and a recycled product. Presently there are approximately 500 million gallons of waste cooking oils generated annually in the United States.
Waste cooking oils are primarily composed of triglycerides with monounsaturated and polyunsaturated fatty acid chains. These unsaturated chains can be thermally polymerized (branched or cross-linked) through intramolecular and intermolecular linkages via oxygen uptake and the Diels-Alder reaction. Heat is needed to accelerate the reaction.
The degree of cross-linking determines the properties of the polymerized oils. Isomerization and the formation of the intra- and intermolecular bonds involved in the thermal process enable designing a product with the appropriate characteristics. The addition of catalyst activates the thermal polymerization of waste cooking oils at lower temperature.